IGCSE Physics 4420/2H Mark Scheme (Results) November 2008

Transcription

1 IGCSE Physics 4420/2H Mark Scheme (Results) November 2008 IGCSE IGCSE Physics (4420/2H) Edexcel Limited. Registered in England and Wales No Registered Office: One90 High Holborn, London WCV 7BH

2 The following acronyms are used owtte ecf dop nwn or words to that effect error carried forward dependent on previous no working necessary 08

3 (a) (A) a.c. (power supply) do not credit just power supply (B) (open) switch / switch which is off (C) (electric) motor (D) variable resistance / rheostat do not credit meter (4) (b) (i) voltmeter voltage/potential difference/p.d. both parts required do not accept voltameter voltemeter voltagemeter etc () (b) (ii) ammeter current/rate of flow of charge both parts required do not accept ampmeter if the meters in both (i) and (ii) are correct award () mark () (Total 6 marks) 08

4 2 (a) 0.5 accept ½ hertz/hz accept (waves) per second 2 (b) light (or any particular named colour of light) (waves) or any member of the electromagnetic S-waves spectrum secondary waves or waves on (slinky) spring shaken/moved up and down () 2 (c) information allow: data /signal () 2 (d) time between one wave and the next or time taken for ea wave to pass (a poin complete/full credit time period i inverse/reciprocal of the frequency with both marks (Total 6 marks) 08

5 3 (a) kinetic thermal/heat sound do not credit just movement, wind or mechanical both required but either order 3 (b) (efficiency) = useful (energy) output ( 00%) total (energy) output/input () 3 (c) either joules/j () or () joules /J () or 45 kilojoules/kj (3) or 5 minutes = 900 s () 50 x 5 = 750 (0) 750 J () (3) (Total 6 marks) 08

6 4 (a) rock or named rock e.g granite, sand etc space cosmic rays Sun nuclear waste radon food water medical sources etc etc allow any reasonable response do not allow (nuclear) power stations or building materials () 4 (b) (i) the card reduces (or stops) the radiation/emission count rate/reading or words to that effect () Question Correct Answer Extra Information Mark 4 (b) (ii) the metal reduces (or stop) the radiation/emission or words to that count rate/reading effect () 4 (b) (iii) (the card and) the metal will not reduce (or stop) the radiation/emission/count rate/reading or words to that effect from gamma /γ (radiation) () 4 (c) 25 (MBq) credit () mark if unambiguous indication that one hour equivalent to four half lives (Total 6 marks) 08

7 5 (a) water is a good conductor (so increases chance of) (electric) shock /current in the body /heart failure or wet skin has a lower (electrical) resistance (than dry skin) Question 5(b) Correct Answer Extra Information Mark (large) current/flow of charge in earth wire melts fuse (wire) (in plug) and cuts off the supply/electricity/current both required for this mark 5 (c) 200 (V) allow () mark for just (V = ) (Total 6 marks) 08

8 6 (a) B () 6 (b) electromagnet () 6 (c) to prevent shorting/a short circuit /to prevent current (accept electricity) from going directly from one turn to the next accept from one coil to the next do not credit any reference to safety/electric shock/heat insulation () 6 (d) gravity accept weight (of the iron sphere) () 6 (e) either clockwise moment = anticlockwise moment or weight.5 = () weight = 90.5 () = 60 () or (weight =) 60 (N) (3) nwn (3) (Total 7 marks) 08

9 7 (a) area of edge (of the blade) is smaller (for a sharp knife) or the converse for a blunt knife either (so) for the same force the pressure (under the blade) will be greater or (so) a smaller force required to give the same pressure (under the blade) 7 (b) (i) two arrows both acting towards the point and no arrows acting away from the point both the same length (as the original line) all right angles dop do not credit anything other than 2 arrows as judged by eye to be a fair attempt 7 (b) (ii) (that the body of the) gas is not moving /stationary/at rest () 7 (c) Use of p = m x g x h () 25 x 025 x 0 () = (Pa) () or (Pa) or (Pa) or answer in kilopascals e.g kpa 25 x 025 (0) (3) (Total 8 marks) 08

10 8 (a) (i) left to right () 8 (a) (ii) electrons have ve charge flow from ve and / or to + ve 8 (b) (i) 0.20 x 3.0 x 240 = 44 (J) 0.2 x 3 x 4 = 2.4 scores (0/2) 8 (b) (ii) thermal/heat () 8 (c) (i) 0.0 x.5 x 240 = 36 (J) / quartered ecf from (b)(i) e.g 0.6(J) 8 (c) (ii) I halved (V halved) () (Total 9 marks) 08

11 9 (a) (i) I correctly labelled () 9 (a) (ii) R correctly labelled () 9 (a) (iii) C correctly labelled () 9 (b) (i) angle at which refraction still/just occurs () 9 (b) (ii) sin c = /n () 9 (b) (iii) c = 38.7(º) () 9 (c) (i) bends more towards normal reflects correctly at glass-air dop 9 (c) (ii) dop refracts more / bends more total internal reflection i > c (Total 0 marks) 08

12 0 (a) = 20 p p = 25 (kpa) 50 x 00 = 30 x p p = 500(kPa) scores 0 (b) constant mass of gas no leaks in or out owtte () 0 (c) (i) bigger () 0 (c) (ii) dop inc in temp molecules move faster owtte (Total 6 marks) 08

13 (a) (i) alpha allow helium nucleus or He with subscript and superscript () (a) (ii) gold nucleus accept metal nucleus () (b) (i) same both + or both - () (b) (ii) repulsion () (c) (i) using sensible scales and correct orientation axes labelled with quantities and units all points plotted correctly smooth curve minimum S/º and d/fm ± mm ( ) per misplot 2 (5) (c) (ii) 35 ± (º) (d) 0º above 90º (e) (i) speed/ kinetic energy momentum () () 08

14 (e) (ii) (alpha) not diverted from its path by particles in air () (f) nuclear allow nucleus () (Total 5 marks) 08

15 2 (a) (i) 0 independent marks 2 (a) (ii) neutron () 2 (b) (i) -β ecf (3) 2 (b) (ii) americium Am only allow Np, Pu, Am, Cu () (Total 7 marks) 08

16 3 (a) (i) slope/gradient () 3 (a) (ii) area (under graph) () 3 (b) (i) no () 3 (b) (ii) dop graph not horizontal or velocity not constant or (still) accelerating () 3 (c) (i) A () 3 (c) (ii) D () 3 (c) (iii) C () Question Correct Answer Extra Information Mark 3 (d) constant velocity weight downwards/drag upwards terminal velocity equal no acceleration (4) 3 (e) greater area under graph before sea (Total 3 marks) 08

17 4 (a) direction () 4 (b) V S S V - for any number of errors up to 2 4 (c) 0.4 N to the right (Total 5 marks) 08

18 5 (a) frequency amplitude speed/wavelength (3) 5 (b) microphone signal generator () 5 (c) alternating waves 2½ cycles or T = 4 squares amplitude = 2 squares ignore quality of drawing (3) 5 (d) any three points B hears due to diffraction C hears due to diffraction C hears due to reflection Or diffraction effect of gap / edge gap about m (3) (Total 0 marks) 08